The present invention relates to measuring vehicle tire air pressure and utilizing these measurements.
The air pressure within inflated vehicle tires is an important parameter for vehicle operation. Vehicle dynamics are closely linked to tire performance. These dynamics affect many aspects of vehicle operation, including handling, braking, rollover characteristics, and the like. Tire pressure also affects the life of the tire. Excess tire pressure may make the tire more susceptible to puncture and, if extreme, to burst damage. Tire under-pressure may result in the generation of excess heat, particularly at elevated vehicle speeds. To ensure proper tire performance, vehicle tires are typically given a range of inflation pressures based on the tire type, vehicle type, vehicle configuration and use, expected driving conditions, and the like. Despite its importance, tire inflation pressure may at times fall outside of specified ranges. Tires often lose air pressure gradually, making the point at which inflation pressure drops below the specified value difficult to detect. Many air pressure gauges for use with vehicle tires are inaccurate, resulting in under-inflation or over-inflation even when proper care is taken. Further, modern run-flat tires provide limited performance even in the presence of substantial pressure loss, making such loss difficult for the vehicle operator to detect.
In-vehicle tire pressure monitoring systems are currently available. Typically, these systems include a tire pressure sensor built into the tire or attached to the tire valve stem. Each sensor relays measured tire pressure to an associated receiver via a wireless link. Tire pressure information is then provided to the vehicle operator by an indicator or graphic display on the vehicle dashboard. Such a display, however, may not solve the problem of out-of-range tire pressure if the display is either unnoticed, misinterpreted, or ignored by the vehicle operator. What is needed is to automatically reduce the effects of out-of-range vehicle tire pressure.
The present invention automatically controls vehicle speed if the vehicle speed is not appropriate for measured tire air pressure.
A system for limiting vehicle speed is provided. The system includes at least one tire pressure sensor. Each tire pressure sensor generates a pressure signal based on the pressure of air within a tire. The system also includes a vehicle speed sensor generating a signal based on the vehicle speed. Control logic generates at least one signal to control the vehicle power plant automatically reducing vehicle speed if that speed is not appropriate for at least one tire based on the sensed tire air pressure.
In an embodiment of the present invention, the system further includes an indicator controlled by the control logic. The indicator indicates automatic speed reduction to the vehicle operator.
In another embodiment of the present invention, each tire pressure sensor generates a signal based on self diagnosis. The control logic inhibits automatic vehicle speed reduction based on sensed tire air pressure in a tire with a pressure sensor generating a failed self diagnosis signal.
In various additional embodiments of the present invention, the control logic automatically reduces vehicle speed if the tire pressure is less than a minimum value, if the tire pressure is less than a value based on the vehicle speed, if the tire pressure is greater than a maximum value, and/or if the tire pressure is greater than a value based on the vehicle speed.
A method of limiting vehicle speed is also provided. Air pressure is sensed in at least one tire. The vehicle speed is sensed. A check is made to determine if vehicle speed is appropriate for each tire based on the sensed tire pressure. If vehicle speed is not appropriate for each tire, the vehicle speed is automatically controlled.
In various embodiments of the present invention, the vehicle speed may be reduced by controlling the delivery of fuel to an engine powering the vehicle, controlling the delivery of spark to an engine powering the vehicle, controlling the delivery of air to an engine powering the vehicle, controlling the revolution rate of a rotating power plant powering the vehicle, and controlling the delivery of electrical power to a motor powering the vehicle.